328 Rain Falling at Rothamsted 



The fall in ammonia and the simultaneous rise in nitrate may of 

 course be wholly unconnected, but it suggests that a former source of 

 ammonia now turns out nitrate instead, or that more nitrate is being 

 produced from ammonia in the air than was previously the case. We 

 have no data for examining the second possibility, but the first has 

 some degree of probability: modern incandescent burners, gas and coal 

 fires, may discharge more nitrous fumes and less ammonia into the 

 atmosphere than the older types. 



Dissolred oxygen in rainwater. 



During the year 1915 estimations of dissolved oxygen in rain at 

 Rothamsted were made^ on rainfalls exceeding 0-30 inch. The great 

 majority of the samples were found to be nearly saturated with oxygen 

 but a few were considerably under saturation, notably those collected 



Mean 11-2 99% 



in July and August. More recent determinations of summer and winter 

 rains gave mean values of 95 and 99 per cent, respectively calculated 

 on Dittmar's figures for distilled water saturated with air at the observed 

 temperature and pressure. It seems possible that the greater height of 



1 This Journal. 1917. 8, 331-337. 



